Posted on by Dr. Francis Collins
Researchers continue to produce impressive miniature human tissues that resemble the structure of a range of human organs, including the livers, kidneys, hearts, and even the brain. In fact, some researchers are now building on this success to take the next big technological step: placing key components of several miniature organs on a chip at once.
These body-on-a-chip (BOC) devices place each tissue type in its own pea-sized chamber and connect them via fluid-filled microchannels into living, integrated biological systems on a laboratory plate. In the photo above, the BOC chip is filled with green fluid to make it easier to see the various chambers. For example, this easy-to-reconfigure system can make it possible to culture liver cells (chamber 1) along with two cancer cell lines (chambers 3, 5) and cardiac function chips (chambers 2, 4).
Researchers circulate blood-mimicking fluid through the chip, along with chemotherapy drugs. This allows them to test the agents’ potential to fight human cancer cells, while simultaneously gathering evidence for potential adverse effects on tissues placed in the other chambers.
This BOC comes from a team of NIH-supported researchers, including James Hickman and Christopher McAleer, Hesperos Inc., Orlando, FL. The two were challenged by their Swiss colleagues at Roche Pharmaceuticals to create a leukemia-on-a-chip model. The challenge was to see whether it was possible to reproduce on the chip the known effects and toxicities of diclofenac and imatinib in people.
As published in Science Translational Medicine, they more than met the challenge. The researchers showed as expected that imatinib did not harm liver cells . But, when treated with diclofenac, liver cells on the chip were reduced in number by about 30 percent, an observation consistent with the drug’s known liver toxicity profile.
As a second and more challenging test, the researchers reconfigured the BOC by placing a multi-drug resistant vulva cancer cell line in one chamber and, in another, a breast cancer cell line that responded to drug treatment. To explore side effects, the system also incorporated a chamber with human liver cells and two others containing beating human heart cells, along with devices to measure the cells’ electrical and mechanical activity separately.
These studies showed that tamoxifen, commonly used to treat breast cancer, indeed killed a significant number of the breast cancer cells on the BOC. But, it only did so after liver cells on the chip processed the tamoxifen to produce its more active metabolite!
Meanwhile, tamoxifen alone didn’t affect the drug-resistant vulva cancer cells on the chip, whether or not liver cells were present. This type of cancer cell has previously been shown to pump the drug out through a specific channel. Studies on the chip showed that this form of drug resistance could be overcome by adding a second drug called verapamil, which blocks the channel.
Both tamoxifen alone and the combination treatment showed some off-target effects on heart cells. While the heart cells survived the treatment, they contracted more slowly and with less force. The encouraging news was that the heart cells bounced back from the tamoxifen-only treatment within three days. But when the drug-drug combination was tested, the cardiac cells did not recover their function during the same time period.
What makes advances like this especially important is that only 1 in 10 drug candidates entering human clinical trials ultimately receives approval from the Food and Drug Administration (FDA) . Often, drug candidates fail because they prove toxic to the human brain, liver, kidneys, or other organs in ways that preclinical studies in animals didn’t predict.
As BOCs are put to work in testing new drug candidates and especially treatment combinations, the hope is that we can do a better job of predicting early on which chemical compounds will prove safe and effective in humans. For those drug candidates that are ultimately doomed, “failing early” is key to reducing drug development costs. By culturing an individual patient’s cells in the chambers, BOCs also may be used to help doctors select the best treatment option for that particular patient. The ultimate goal is to accelerate the translation of basic discoveries into clinical breakthroughs. For more information about tissue chips, take a look at NIH’s Tissue Chip for Drug Screening program.
 Multi-organ system for the evaluation of efficacy and off-target toxicity of anticancer therapeutics. McAleer CW, Long CJ, Elbrecht D, Sasserath T, Bridges LR, Rumsey JW, Martin C, Schnepper M, Wang Y, Schuler F, Roth AB, Funk C, Shuler ML, Hickman JJ. Sci Transl Med. 2019 Jun 19;11(497).
 Clinical development success rates for investigational drugs. Hay M, Thomas DW, Craighead JL, Economides C, Rosenthal J. Nat Biotechnol. 2014 Jan;32(1):40-51.
Tissue Chip for Drug Screening (National Center for Advancing Translational Sciences/NIH)
James Hickman (Hesperos, Inc., Orlando, FL)
NIH Support: National Center for Advancing Translational Sciences
Posted on by Dr. Francis Collins
Scientists first described the sickle-shaped red blood cells that give sickle cell disease its name more than a century ago. By the 1950s, the precise molecular and genetic underpinnings of this painful and debilitating condition had become clear, making sickle cell the first “molecular disease” ever characterized. The cause is a single letter “typo” in the gene encoding oxygen-carrying hemoglobin. Red blood cells containing the defective hemoglobin become stiff, deformed, and prone to clumping. Individuals carrying one copy of the sickle mutation have sickle trait, and are generally fine. Those with two copies have sickle cell disease and face major medical challenges. Yet, despite all this progress in scientific understanding, nearly 70 years later, we still have no safe and reliable means for a cure.
Recent advances in CRISPR/Cas9 gene-editing tools, which the blog has highlighted in the past, have renewed hope that it might be possible to cure sickle cell disease by correcting DNA typos in just the right set of cells. Now, in a study published in Science Translational Medicine, an NIH-funded research team has taken an encouraging step toward this goal . For the first time, the scientists showed that it’s possible to correct the hemoglobin mutation in blood-forming human stem cells, taken directly from donors, at a frequency that might be sufficient to help patients. In addition, their gene-edited human stem cells persisted for 16 weeks when transplanted into mice, suggesting that the treatment might also be long lasting or possibly even curative.